1. Chapter 6: Introduction to Genetics
Section 6-1:
The Science of Inheritance and
Gregor Mendel

2. Parents and Offspring Heredity = biological inheritance
An organism’s heredity is the set of characteristics it receives from its parents.
Genetics is the study of heredity.
Heredity IS NOT just a blend of characteristics from both parents – look at page 124

3. Gregor Mendel
Born in 1822, became a monk, but also studied science and math in Vienna
In the monastery, Mendel’s job was to take care of the garden (monasteries are self-sustaining)
He took an interest in pea plants – he began with true-breeding stock

4. True-Breeding Stock
True-breeding stock refers to individuals that always pass on their characteristics to the next generation (ex. a tall pea plant with green pods will ALWAYS produce tall pea plants with green pods)

5. Reproduction in Pea Plants
Peas use their flowers to reproduce (p.125)
Male sex cell = pollen
Female sex cell = egg
Pea plants normally self-pollinate, meaning the pollen and egg come from the same plant (basically only one parent)
True-breeding stock results from generations of self-pollination

6. Mendel and Pea Plants
Mendel wanted to see what would happen if he crossed true-breeding stock with different characteristics
Mendel removed all the male plant parts so that he could control pollination, making sure that pollen and egg came from different plants
This is called cross-pollination

7. Mendel’s Seven Traits
Trait = characteristic that identifies one individual from another
Mendel focused on seven traits, each with two contrasting forms

8. Mendel’s Seven Traits Trait Form 1 Form 2 Seed shape Round Wrinkled
Seed color
Yellow
Green
Seed coat color
Gray
White
Pod shape
Smooth
Constricted
Pod color
Flower position
Axial
Terminal
Plant height
Tall
Short

9. Mendel’s Seven Traits
Mendel used true-breeding stock to create hybrids – offspring of parents with different characteristics
The hybrids were called the first filial generation (F1 generation) and the true-breeding stock were called the parental generation (P generation)

10. Mendel’s Seven Traits
Mendel noticed the traits seen in the F1 generation were not a blending of the P generation’s traits
The traits of only ONE parent appeared in the offspring while the traits of the other parent seemed to disappear